Weight

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tatanab
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Re: Weight

Postby tatanab » 26 Jun 2014, 2:11pm

I had a "sunny Sunday special" until a couple of years ago. A 1970s time trial bike on tubs and so on. I sold it because I just wasn't using it. Similarly I lust after a steel Colnago, but I know I simply have no use for it.

Phone versus tools. Tools always work whereas the phone is no good if there is nobody on the other end to pick it up. I prefer to be self sufficient rather shivering at the side of the road. I don't even routinely carry a phone (shock, horror, how can you......, what if....... = modern generation response to that).

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Trigger
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Re: Weight

Postby Trigger » 26 Jun 2014, 2:33pm

tatanab wrote: I don't even routinely carry a phone (shock, horror, how can you......, what if....... = modern generation response to that).


There's a difference though between "well we never had phones when I were a lad, so I'll be reet" and it being a very handy tool to carry with no downsides, it's a no brainer to carry one IMO, and I'm not young.

Ray
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Re: Weight

Postby Ray » 26 Jun 2014, 2:41pm

Trigger wrote:There's a difference though between "well we never had phones when I were a lad, so I'll be reet" and it being a very handy tool to carry with no downsides, it's a no brainer to carry one IMO, and I'm not young.

We never had mobile phones . . . but we did have a lot more red phone boxes on street corners.
I always carry a mobile now.

Edited to add: Oh, and a pump, and a couple of spare inner tubes and a small multi-tool.
Ray
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt - Bertrand Russell

Ray
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Re: Weight

Postby Ray » 26 Jun 2014, 2:56pm

I doubt that 'weight weenies' carry much, if anything, in the way of tools but, if they did, they might be interested in my latest multi-tasking gadget from PlanetX -

minimultitool.png
minimultitool.png (23.77 KiB) Viewed 383 times

Bought on the basis of years of experience that a chain tool has been used fairly often - well, maybe an average of once every 4 or 5 yrs :D - and most often on other people's bikes.

A friend and I did once re-join a chain using a couple of rocks, but one of these would have been better!
Ray
The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt - Bertrand Russell

Brucey
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Re: Weight

Postby Brucey » 26 Jun 2014, 3:32pm

Trigger wrote:
tatanab wrote: I don't even routinely carry a phone (shock, horror, how can you......, what if....... = modern generation response to that).


There's a difference though between "well we never had phones when I were a lad, so I'll be reet" and it being a very handy tool to carry with no downsides, it's a no brainer to carry one IMO, and I'm not young.


I had a prang recently and several of my chums (who lived not far away) asked why I didn't call them. 'No phone' I said. They maintained it was 'ridiculous' etc that I wasn't carrying one, until I asked them what use it might have been in the same state as the things that were in my pockets at the time; i.e. all smashed to pieces.

cheers
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recordacefromnew
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Re: Weight

Postby recordacefromnew » 26 Jun 2014, 3:47pm

Brucey wrote:
recordacefromnew wrote:.... one can simply use the formula of kinetic energy (which is converted to potential energy stored in vertical elevation) to estimate the impact on speed. Since kinetic energy is directly proportion to mass but square of speed, an increase (say 10%) in rider+bike mass will be cancelled by a reduction in speed of only roughly 4.6%....


This isn't right at all. If you are going to neglect air resistance then power required for climbing is very simply proportional to speed.

cheers


Brucey you are usually right, but not this time. :D

It is true power required for climbing is simply proportional to speed, but that is an irrelevant fact isn't it, when we are talking about the effect of mass on speed in climbs. If we don't keep power constant (and all else being equal), we will be introducing a 3rd variable, which is going to muddy the water at best, and lead to a wrong conclusion at worst, rather than clarify the issue. Perhaps that is where McCraw went wrong too.

OnYourRight
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Re: Weight

Postby OnYourRight » 26 Jun 2014, 4:06pm

squeaker wrote:Can always have a play on here if you are that interested :wink:

It’s interesting, if not hugely surprising, that using the drops reduces so greatly the power needed.

recordacefromnew wrote:It is true power required for climbing is simply proportional to speed, but that is an irrelevant fact isn't it, when we are talking about the effect of mass on speed in climbs.

But why? If we’re ignoring air resistance (and rolling resistance), which seems a reasonable simplification at the very low speeds of steep climbs, then our power is just applied to lifting a mass against gravity. Halve that mass and the climbing rate would simply double. I think kinetic energy is a red herring here: it remains constant at constant speed and can therefore be ignored. We’re just concerned with gravitational potential energy.

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Trigger
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Re: Weight

Postby Trigger » 26 Jun 2014, 4:08pm

Brucey wrote:
Trigger wrote:
tatanab wrote: I don't even routinely carry a phone (shock, horror, how can you......, what if....... = modern generation response to that).


There's a difference though between "well we never had phones when I were a lad, so I'll be reet" and it being a very handy tool to carry with no downsides, it's a no brainer to carry one IMO, and I'm not young.


I had a prang recently and several of my chums (who lived not far away) asked why I didn't call them. 'No phone' I said. They maintained it was 'ridiculous' etc that I wasn't carrying one, until I asked them what use it might have been in the same state as the things that were in my pockets at the time; i.e. all smashed to pieces.

cheers


I carry mine in my rack pack, wrapped up in my water proof, if I ever have a crash big enough to smash up my phone then I'll probably be dead anyway so it won't be much use :lol:

Brucey
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Re: Weight

Postby Brucey » 26 Jun 2014, 4:21pm

recordacefromnew wrote:
Brucey you are usually right, but not this time. :D

It is true power required for climbing is simply proportional to speed, but that is an irrelevant fact isn't it, when we are talking about the effect of mass on speed in climbs.


go read a basic physics text; (again neglecting air resistance, at constant speed), power for climbing is also proportional to weight.

cheers
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recordacefromnew
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Re: Weight

Postby recordacefromnew » 26 Jun 2014, 4:39pm

OnYourRight wrote:
recordacefromnew wrote:It is true power required for climbing is simply proportional to speed, but that is an irrelevant fact isn't it, when we are talking about the effect of mass on speed in climbs.

But why? If we’re ignoring air resistance (and rolling resistance), which seems a reasonable simplification at the very low speeds of steep climbs, then our power is just applied to lifting a mass against gravity. Halve that mass and the climbing rate would simply double. I think kinetic energy is a red herring here: it remains constant at constant speed and can therefore be ignored. We’re just concerned with gravitational potential energy.


Brucey wrote:
recordacefromnew wrote:
Brucey you are usually right, but not this time. :D

It is true power required for climbing is simply proportional to speed, but that is an irrelevant fact isn't it, when we are talking about the effect of mass on speed in climbs.


go read a basic physics text; (again neglecting air resistance, at constant speed), power for climbing is also proportional to weight.

cheers


You are of course right. Apologies to all! :oops:

iandriver
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Re: Weight

Postby iandriver » 26 Jun 2014, 4:57pm

Any special reason why you'd want to go faster? 10 and a bit kilos and a few tools isn't exactly a dog. Unless your hopes and dreams are pinned on winning races and you are getting up hills OK, who really gives a rats? (Am I the only one who stops mid Audax for a go on the village slide and swings? :oops: ).
Supporter of the A10 corridor cycling campaign serving Royston to Cambridge http://a10corridorcycle.com. Never knew gardening secateurs were an essential part of the on bike tool kit until I took up campaigning.....

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Mick F
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Re: Weight

Postby Mick F » 26 Jun 2014, 5:22pm

Brucey wrote:..... power for climbing is also proportional to weight.
I don't doubt this for one second.

If power is a constant, what weight equals what speed reduction?

Could it be that an extra 100g would make an appreciable difference to a normal rider on a normal hill on a normal bike?
Somehow I doubt it.
Mick F. Cornwall

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mjr
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Re: Weight

Postby mjr » 26 Jun 2014, 6:49pm

iandriver wrote:(Am I the only one who stops mid Audax for a go on the village slide and swings? :oops: ).

Change "Audax" to "ride" and it sounds like the sort of stuff I do. :lol:
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.

reohn2
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Re: Weight

Postby reohn2 » 26 Jun 2014, 6:56pm

iandriver wrote:Any special reason why you'd want to go faster? ......


That's a very good question,because unless you're trying to win races it doesn't matter about the equipement.
There's no meaning to beating your PB against the clock,if the difference is a supermarket special on the one hand and 5K TT bike on the other.
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Brucey
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Re: Weight

Postby Brucey » 26 Jun 2014, 8:20pm

Mick F wrote:
Brucey wrote:..... power for climbing is also proportional to weight.
I don't doubt this for one second.

If power is a constant, what weight equals what speed reduction?

Could it be that an extra 100g would make an appreciable difference to a normal rider on a normal hill on a normal bike?
Somehow I doubt it.


It won't be a big difference in speed if it isn't a big difference in weight. On a steep climb (where air resistance and rolling resistance are a small fraction of the overall drag) a 1% weight reduction might make for almost 1% increase in speed.

Tyres count more than that, not least because lighter ones normally roll easier.

cheers
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